The new study is based on data from the Childhood Cancer Survivor Study. The study followed five-year survivors from 26 institutions who were under 21 when diagnosed with cancer. Researchers studied 3,531 sexually active women, age 18-39, who survived cancer and compared them to a group of 1,366 female siblings who did not have cancer.

Overall, 15.9 percent of women who survived childhood cancer were affected by infertility, with 12.9 percent trying to conceive for at least one year without success. (The remaining cancer survivors included in the infertile group had experienced ovarian failure and may not have even attempted pregnancy.) Compared to their siblings, the cancer survivors had a 50 percent higher risk of infertility. Despite higher rates of infertility, nearly two-thirds of cancer survivors conceived, on average, after another six months. Among the comparison group of clinically infertile siblings, it took another five months to conceive, on average.

Women whose cancer was treated with alkylating agent chemotherapy or high-dose radiation to the abdomen or pelvis were at greatest risk of infertility. Although pediatric oncologists have changed a number of treatment protocols over the last several decades, alkylating agents and radiation continue to be used. Researchers hope the study results will help physicians offer guidance to patients about fertility based on their cancer treatment protocol.

“Women who have a history of childhood cancer treatment should consider themselves likely to be fertile. However, it might be important to see an expert sooner rather than later if a desired pregnancy doesn’t happen within the first six months,” concludes Dr. Lisa Diller, senior author of the study, chief medical officer of Dana-Farber/Boston Children’s, and medical director of the David B. Perini, Jr. Quality of Life Clinic at Dana-Farber Cancer Institute.